add more descriptive errors

Signed-off-by: Tw <tw19881113@gmail.com>

caddyhttp/gzip/gzip.go

@@ -5,7 +5,6 @@ package gzip
 import (
 	"bufio"
 	"compress/gzip"
-	"fmt"
 	"io"
 	"io/ioutil"
 	"net"
@@ -144,7 +143,7 @@ func (w *gzipResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
 	if hj, ok := w.ResponseWriter.(http.Hijacker); ok {
 		return hj.Hijack()
 	}
-	return nil, nil, fmt.Errorf("not a Hijacker")
+	return nil, nil, httpserver.NonHijackerError{Underlying: w.ResponseWriter}
 }
 
 // Flush implements http.Flusher. It simply wraps the underlying
@@ -153,7 +152,7 @@ func (w *gzipResponseWriter) Flush() {
 	if f, ok := w.ResponseWriter.(http.Flusher); ok {
 		f.Flush()
 	} else {
-		panic("not a Flusher") // should be recovered at the beginning of middleware stack
+		panic(httpserver.NonFlusherError{Underlying: w.ResponseWriter}) // should be recovered at the beginning of middleware stack
 	}
 }
 
@@ -163,5 +162,5 @@ func (w *gzipResponseWriter) CloseNotify() <-chan bool {
 	if cn, ok := w.ResponseWriter.(http.CloseNotifier); ok {
 		return cn.CloseNotify()
 	}
-	panic("not a CloseNotifier")
+	panic(httpserver.NonCloseNotifierError{Underlying: w.ResponseWriter})
 }

caddyhttp/header/header.go

@@ -5,7 +5,6 @@ package header
 
 import (
 	"bufio"
-	"errors"
 	"net"
 	"net/http"
 	"strings"
@@ -123,5 +122,5 @@ func (rww *responseWriterWrapper) Hijack() (net.Conn, *bufio.ReadWriter, error)
 	if hj, ok := rww.w.(http.Hijacker); ok {
 		return hj.Hijack()
 	}
-	return nil, nil, errors.New("not a Hijacker")
+	return nil, nil, httpserver.NonHijackerError{Underlying: rww.w}
 }

caddyhttp/httpserver/error.go

@@ -0,0 +1,44 @@
+package httpserver
+
+import (
+	"fmt"
+)
+
+var (
+	_ error = NonHijackerError{}
+	_ error = NonFlusherError{}
+	_ error = NonCloseNotifierError{}
+)
+
+// NonHijackerError is more descriptive error caused by a non hijacker
+type NonHijackerError struct {
+	// underlying type which doesn't implement Hijack
+	Underlying interface{}
+}
+
+// Implement Error
+func (h NonHijackerError) Error() string {
+	return fmt.Sprintf("%T is not a hijacker", h.Underlying)
+}
+
+// NonFlusherError is more descriptive error caused by a non flusher
+type NonFlusherError struct {
+	// underlying type which doesn't implement Flush
+	Underlying interface{}
+}
+
+// Implement Error
+func (f NonFlusherError) Error() string {
+	return fmt.Sprintf("%T is not a flusher", f.Underlying)
+}
+
+// NonCloseNotifierError is more descriptive error caused by a non closeNotifier
+type NonCloseNotifierError struct {
+	// underlying type which doesn't implement CloseNotify
+	Underlying interface{}
+}
+
+// Implement Error
+func (c NonCloseNotifierError) Error() string {
+	return fmt.Sprintf("%T is not a closeNotifier", c.Underlying)
+}

caddyhttp/httpserver/recorder.go

@@ -2,7 +2,6 @@ package httpserver
 
 import (
 	"bufio"
-	"errors"
 	"net"
 	"net/http"
 	"time"
@@ -75,7 +74,7 @@ func (r *ResponseRecorder) Hijack() (net.Conn, *bufio.ReadWriter, error) {
 	if hj, ok := r.ResponseWriter.(http.Hijacker); ok {
 		return hj.Hijack()
 	}
-	return nil, nil, errors.New("not a Hijacker")
+	return nil, nil, NonHijackerError{Underlying: r.ResponseWriter}
 }
 
 // Flush implements http.Flusher. It simply wraps the underlying
@@ -84,7 +83,7 @@ func (r *ResponseRecorder) Flush() {
 	if f, ok := r.ResponseWriter.(http.Flusher); ok {
 		f.Flush()
 	} else {
-		panic("not a Flusher") // should be recovered at the beginning of middleware stack
+		panic(NonFlusherError{Underlying: r.ResponseWriter}) // should be recovered at the beginning of middleware stack
 	}
 }
 
@@ -94,5 +93,5 @@ func (r *ResponseRecorder) CloseNotify() <-chan bool {
 	if cn, ok := r.ResponseWriter.(http.CloseNotifier); ok {
 		return cn.CloseNotify()
 	}
-	panic("not a CloseNotifier")
+	panic(NonCloseNotifierError{Underlying: r.ResponseWriter})
 }

caddyhttp/proxy/proxy_test.go

@@ -97,6 +97,39 @@ func TestReverseProxyInsecureSkipVerify(t *testing.T) {
 	}
 }
 
+func TestWebSocketReverseProxyNonHijackerPanic(t *testing.T) {
+	// Capture the expected panic
+	defer func() {
+		r := recover()
+		if _, ok := r.(httpserver.NonHijackerError); !ok {
+			t.Error("not get the expected panic")
+		}
+	}()
+
+	var connCount int32
+	wsNop := httptest.NewServer(websocket.Handler(func(ws *websocket.Conn) { atomic.AddInt32(&connCount, 1) }))
+	defer wsNop.Close()
+
+	// Get proxy to use for the test
+	p := newWebSocketTestProxy(wsNop.URL)
+
+	// Create client request
+	r, err := http.NewRequest("GET", "/", nil)
+	if err != nil {
+		t.Fatalf("Failed to create request: %v", err)
+	}
+	r.Header = http.Header{
+		"Connection":            {"Upgrade"},
+		"Upgrade":               {"websocket"},
+		"Origin":                {wsNop.URL},
+		"Sec-WebSocket-Key":     {"x3JJHMbDL1EzLkh9GBhXDw=="},
+		"Sec-WebSocket-Version": {"13"},
+	}
+
+	nonHijacker := httptest.NewRecorder()
+	p.ServeHTTP(nonHijacker, r)
+}
+
 func TestWebSocketReverseProxyServeHTTPHandler(t *testing.T) {
 	// No-op websocket backend simply allows the WS connection to be
 	// accepted then it will be immediately closed. Perfect for testing.

caddyhttp/proxy/reverseproxy.go

@@ -21,6 +21,8 @@ import (
 	"strings"
 	"sync"
 	"time"
+
+	"github.com/mholt/caddy/caddyhttp/httpserver"
 )
 
 var bufferPool = sync.Pool{New: createBuffer}
@@ -189,7 +191,7 @@ func (rp *ReverseProxy) ServeHTTP(rw http.ResponseWriter, outreq *http.Request,
 		res.Body.Close()
 		hj, ok := rw.(http.Hijacker)
 		if !ok {
-			panic("not a hijacker")
+			panic(httpserver.NonHijackerError{Underlying: rw})
 		}
 
 		conn, _, err := hj.Hijack()